Control system for hydraulic motor units



Oct. 23, 1956 R LAPsLEY 2,767,550

CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITS Filed NOV. 18, 1954 2Sheets-Sheet 1 FIG. I

INVENTOR. ROBERT LAPSLEY m hwg mpm ATTY.

Oct. 23, 1956 R. LAPSLEY 2,767,550

CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITS Filed Nov. 18, 1954 2Sheets-Sheet FIG; 2

IN V EN TOR. ROBERT LAPSLEY BY I ATTY.

United States Patent 2,767,550 CONTROL SYSTEM FOR HYDRAULIC MOTOR UNITSRobert Lapsley, Buchanan, Mich, assignor to Clark Equipment Company, acorporation of Michigan Application November 18, 195%, Serial No.469,760 5 Claims. (Cl. 60-97) My present invention relates to ahydraulic system for controlling a plurality of hydraulic units whichmay for example be found embodied in industrial fork lift trucks.

Presently, a number of hydraulic units are embodied in conventionalindustrial fork lift trucks for tilting the uprights, elevating the loadsupporting carriage and actuating auxiliary load engaging devicesmounted to the latter. These hydraulic units are supplied with operatingfluid from a single source of fluid pressure or pump. This system isunsatisfactory because of the ditference in capacitiesbetween theseveral hydraulic units. The hydraulic unit which serves to operate theload supporting carriage is of large capacity and requires a relativelylarge fluid flow, while the other hydraulic units are of small capacityand require only a relatively small fluid flow.

Obviously the single pump must be of relatively large capacity toproperly operate the large capacity hydraulic unit. However, such alarge capacity pump does not permit the proper operation of the smallcapacity hydraulic units since it is difiicult to tap-ofl a small supplyof fluid pressure from a large supply source with any degree ofconsistently smooth results. The pump delivers such a large amount offluid that as valve means is opened for directing fluid to a smallcapacity hydraulic unit there is a sudden surge of fluid and operationis begun with a jerk. Such improper operation frequently causes damageto the hydraulic units, the truck or the load carried thereby.

It is an object of my present invention to provide a hydraulic systemwhich may be actuated to provide different amounts of fluid underpressure for properly operating any one of aplurality of hydraulic unitsat least one of which requires a relatively large fluid flow and atleast another of which requires only a relatively small I accomplish theabove object by providing a hydraulic system with two sources of fluidpressure. The fluid delivered by both sources is selectively employedfor actuating the hydraulic unit requiring the relatively large fluidflow and the fluid delivered by only one source is selectively employedfor actuating one of the hydraulicunits requiring the relatively smallfluid flow. With this system, damage due to actuation of the hydraulicunits is eliminated since the latter each can be provided with theproper amount of fluid under pressure for smooth operation. As will bedescribed in detail hereinafter, I

have also provided novel valve means which is particularly adapted foruse in my above described hydraulic system.

Now, in order to acquaint those skilled in the art with the manner ofconstructing and using hydraulic system in accordance with theprinciples of my present invention,

I shall describe in connection with the accompanying drawings, apreferred embodiment of my invention.

In the drawings:

Figure 1 is a diagrammatic showing of the hydraulic control system of mypresent invention; and

Figure 2 is a sectional view of the valve means employed in thehydraulic control system of Figure 1.

Referring now to the drawings, I shall describe the hydraulic controlsystem of my present invention which comprises a pump assembly indicatedgenerally by the reference numeral 10. The pump assembly 10 provides twosources of fluid pressure and may take the form of two separate pumpsor, as shown, of a unitary dual unit pump, such as is disclosed andclaimed in my copending application, Serial No. 454,673, filed September8, 1954. More specifically, the pump assembly 10 has a single commoninlet 12 and a pair of separate outlets 14 and 16. The path of fluidflow through the pump assembly is illustrated by the dot-dash lines inFigure 1.

The inlet 12 of the pump assembly 10 is connected through piping 18 to afluid supply or sump tank 20.

To protect the elements of the hydraulic system and the hydraulic unitsoperated thereby, relief valves 22 and 24 are mounted respectively atthe pump outlets 14 and 16. The relief valves 22 and 24 are connectedwith the sump tank 20 through fluid lines 26 and 28 for bypassing fluidback to the sump tank 20 in the event that the pressure of the fluidbeing delivered by the pump assembly 10 exceeds a predetermined maximumsafe value.

As will be presently described, the relief valves 22 and 24 permitfluid, which is of a pressure less than the predetermined maximum safevalue, to pass therethrough for delivery to the control valve means ofmy present invention which is shown diagrammatically in Figure 1 and incross-section in Figure 2. As will be understood by those skilled in theart, the several sections of the control valve means may be formedindependently and joined by suitable piping or may be formed in aunitary valve housing 32 with internal passageways such as shown inFigure 2.

The relief valve 22 is connected by means of a fluid passageway 30 withone end of the valve housing 32, while the relief valve 24 is connectedby means of a fluid passageway 34 with one side of the valve housing 32'parallel, spaced The valve open- The control valve means includes fourapart valve openings 36, 38, 40 and 42. ing 36 is formed with axiallyspaced annular grooves 44, 45, 46, with axially spaced annular grooves50, 51, 52, 53 and 54; the valve opening 40 is formed with axiallyspaced annular grooves 56, 57 and 58; and the valve opening 42 is formedwith annular grooves 60, 61 and 62. Axially slideab'le spool valves 64,66, 68 and 7t) are disposed. and' respectively in thevalve openings 36,38, 40 and 42 constitute the valve units 72, 74, 76 and 78.

The aforedescribed fluid passageway 38, as shown in'th'e drawings,communicates with the annular grooves 45 and 47 in the valve opening 36,while the annular groove 46 communicates through a fluid passagewaySllwith the annular grooves 51 and 53 in the valve opening 38.

The annular groove 52 in the valve opening 38 communicates through afluid passageway 82 with the. an-

nular groove 57 in the valve opening 40. The afore-.

one ends with the annular groove 56 in the valve open ing 40 and withthe annular groove 62 in the valve opening 42. The other ends. of thefluid passageways 84 and 86 connect with a common fluid passageway 88which, as shown in Figure 1, is connected with the sump tank 20.

The annular grooves 44 and 48 in the valve opening 36 and the annulargrooves 50 and 54 in the valveopening 38 are adapted to be respectivelyconnected, through fluid lines 81 Patented Oct. 23, 1956 47 and 48; thevalve opening 38 is formed,

and 83, and and 87, to the opposite ends of double-acting hydraulicallyactuated units, while the-annular groove 69 inthe valve opening to beconnected, through a fluid line 89, to the one end of a single-actinghydraulic unit. The single-acting unit may, forexarnple constitute thehydraulic piston' and cylinder assembly which is incorporatedinart-industrial lift truck for elevating the load supporting carriage ofthe truck. Fluid need only be forced into the lower end of the cylinderof the hydraulic assembly to cause upward movement of the loadsupporting carriage, the weight of the assembly being relied-on toeflcct lowering of the carriage when fluid is bled from the cylinder ofthe hydraulic assembly. The double-acting'units may constitute hydraulicpiston cylinder assemblies which are incorporated in industrial lifttruck foreffecting tilt of the uprights or actuation of auxiliarydevices such as load clamps or load shifters secured to the loadsupporting carriage. In the applications of the hydraulic units noted,the double-acting units are of small capacity and require only arelatively small fluid flow, while the single-acting unit is of largecapacity and requires a relatively large fluid flow. Because theconstruction and operation of hydraulic units, industrial lift trucksand auxiliary devices therefor are well known to those in the materialhandling field and since they do not constitute part of my presentinvention, it is thought to be unnecessary to include a showing anddescription thereof in the present disclosure.

Returning now to the spool valves, it will be noted that the valve 64 isformed with axially spaced annular channels 90 and 92; that the valve 66is formed with axially spaced annular channels 94 and 96; and that thevalves 68 and 70 are formed respectively with annular channels 98 and100. Incorporated with the ends of the valves 64, 66, 68 and 70 areaxially extendingstems 102, 104, 106 and 108 which are pivotallyconnected to links 110, 112, 114 and 116. The links 110 and 112, inturn, are respectively pivotally connected to actuating 1evers118 and120 which are fulcrumed M122 and 124, while the links 114 and 116 arepivotally connected to a common actuating lever 126 which is fulcrumedat 128. From the foregoing description, it will be realized that thevalves 64 and 66 may be moved axially independently of each other andofvalves 68 and 70, while the valves 68 and 70 may be movedsimultaneously axially in opposite directions, but independently ofvalves 64 and 66.

The valve housing 32 may be enclosed in a fluid tight casing and allvented fluid returned to the sump tank 20 through a return line (notshown). Alternatively, in some applications, the valve housing 32 may bemountedin the sump tank 20 so as to eliminatefluid return lines.

I shall. now describe the operation of the hydraulic system of mypresent invention wherein the fluid delivered by one unit of the pumpassembly may be used for actuating the small capacity hydraulic unitconnected with either the valve unit 72 or the valve unit 74, or thefluid delivered by both pump units may be used to actuate the largecapacity hydraulic unit connected with the valve units 76 and 78.

When the valves 64, 66, 68 and70 are in theirneutral or mid-pointpositions, as shown in Figure 2, fluid under pressure flowing throughthe passageway 30 from the one pump unit is returned to the sumptank'20through the interconnecting annular grooves 45 and 47, annularchannels 90'and 92, passageway 80, annular grooves 51 and 53, annularchannels 94 and 96, passageway 82,.annular groove 57, annular channel98, annular groove 56, and passageways 84 and 88; Also, fluid underpressure delivered through the passageway 34 from the. other pump unitis returned to the sump tank through passageway 59, annular groove 61,annular channel 100, annular groove 62, and passageways 86' and 88.

Should it be desired to effect actuation of. the hydraulic unitassociated with the control valve unit 72, the actuat- 42- is adapted iing lever 118 need only be pivoted about the fulcrum 122- for axiallymoving the valve 64 in one direction or the other. If the lever 118 ispivoted clockwise from the position shown in Figure 2, the valve 64 ismoved to the right, communication between the passageways 30 and isblocked by the body of valve 64, and fluid is directed from thepassageway 30 through the annular channel 92 to the annular groove 48which is connected to one end ofthe hydraulic unit by fluid line 83.Simultaneously the body of valve 64 is moved away from the annulargroove 44 and thus the latter communicates outwardly of the valvehousing 32 for bleeding fluid from the other end of the hydraulic unitconnected to the fluid line 81. At such time as the hydraulic unit hasbeen actuated the desired amount, the valve 64 may be returned to theneutral position shown in Figure 2 thus blocking fluid flow to or fromthe hydraulic unit until the valve 64 is further actuated.

If the hydraulic unit associated withthe valve unit 72 is to be actuatedin a direction opposite to that just described, the lever 118 is pivotedin a counterclockwise direction for moving the valve 64 axially to theleft. When the valve 64 is moved to the left, communication between thepassageways 30 and 80 is again blocked by the body of valve 64 and fluidis directed from the passageway 30through the annular channel 90 to theannular groove 44 which is connected to the other end of the hydraulicunit by fluid line 81. Simultaneously, the body of the valve 64 isremoved from register with the annular groove 48 whereupon the latter ispermitted to open outwardly of the valve housing 32 so as to allow fluidto drain from the one end of the hydraulic unit connected to the fluidline 83. As noted, actuation of the hydraulic unit may be interrupted atany time by returning the valve 64 to the position shown in Figure 2.

When the valve 64 is maintained in its neutral position, the valve 66may be actuated by the lever 120 for controlling operation of thehydraulic unit associated with the control valve unit 74. The valve 66is controlled and operates in the same manner as the valve 64. It servesto place passageway 80 into communication with either annular groove 50and fluid line or annular groove 54 and fluid line 87. In eitherposition communication between the passageways 80 and 82 is interrupted.

It is to be noted that whenever the valve 64 or 66 is actuated while thevalve 68 and 70 are maintained in a neutral position, only fluid underpressure the passageway 30 from one of the pump units is directed to thehydraulic unit associated with the respective valve unit 72 or 74. Thefluid under pressure flowing through the passageway 34 from the otherpump unit is returned directly to the sump tank as aforedescribed,through the passageway 59, annular groove 61, annular channel 100,annular groove 62, and fluid passageways 86 and 88.

When it is desired to effect operation of the hydraulic unit associatedwith the control units 76 and 78, the valves 64 and 66 are placed in theneutral positions shown in Figure 2, and the valve 68 is moved to theright while i the valve 70 is moved to the left through clockwisemovement of the actuating lever 126 about fulcrum 128. When the valves66 and 68 are so moved, fluid under pressure delivered by bothof thepump units is directed to the hydraulic unit connected with the annulargroove 60 through fluid line 89. Fluid flows from the passageway 34 tothe annular groove'60 through the passageway 59, annular groove 61 andannular channel 100. Also, fluidiflows from the passageway 30 to theannular groove 60 through the annular grooves 45 and 47, annularchannels 90 and 92,, annular groove 46, passageway 80, annular grooves51 and 53, annular channels 94 and 96, an-

nular groove 52, passageway 82, annular groove 57, 3th,

nular channel 98, annular groove 58, passageway 59, annular groove 61,and annular channel 100. i

Once fluid has been delivered to the hydraulic unit flowing through iassociated with the valve units 76 and 78 it may be maintained ortrapped therein by returning the valves 68 and 70 to the positions shownin Figure 2 so that the body of the valve 70 will block the annulargroove 60. Should it then become desirable to bleed fluid from thehydraulic unit, the actuating lever 126 need only be pivotedcounterclockwise from the position shown in Figure 2 for moving the bodyof the valve 76 out of register with the annular groove 60 so as topermit the latter to communicate outwardly of the valve housing 32.After the desired amount of fluid has been bled from the hydraulic unit,the valves 68 and 70 may be returned to the neutral positions shown inFigure 2.

In conclusion, the hydraulic system of my present invention providescontrol for a plurality of hydraulic units one of which requires arelatively large fluid flow and the others of which require only arelatively small fluid flow. Two sources of fluid pressure are providedwith the fluid delivered by both sources being selectively employed foractuating the hydraulic unit requiring the relatively large fluid flowand with the fluid delivered by one source being selectively employedfor actuating one of the hydraulic units requiring the relatively smallfluid flow. This arrangement is such that different amounts of fluidunder pressure are readily available for distribution to a plurality ofhydraulic units of different capacity. Thus, the several hydraulic unitsmay be operated smoothly, and damage due to operation of the hydraulicunits eliminated.

Now, while I have shown and described what I believe to be a preferredembodiment of my present invention, it will be understood by thoseskilled in the art that various rearrangements and modifications may bemade therein without departing from the spirit and scope of myinvention.

I claim:

1. A hydraulic system for controlling actuation of first and secondhydraulic units comprising the combination of a pump assembly having twoseparate outlets and a common inlet connected with a sump tank, fluidpassageway means extending between said pump outlets and the first andsecond hydraulic units and said sump tank, first and second valve meansinterposed in said fluid passageway means and having neutral positionswherein fluid under pressure delivered by said pump assembly ispermitted to return directly to said sump tank, said first valve meanswhen moved from a neutral position being operable to permit fluid underpressure to flow from one of said pump outlets through said fluidpassageway means to the first hydraulic unit, and said second valvemeans when moved from a neutral position being operable to permit fluidunder pressure to flow from both of said pump outlets through said fluidpassageway mans to the second hydraulic unit when said first valve meansis in neutral.

2. A hydraulic system for controlling actuation of first and secondhydraulic units comprising the combination of a pump assembly having twoseparate outlets and an inlet connected with a sump tank, first fluidpassageway means extending between one of said pump outlets and saidsump ta first valve means operable to interrupt communication betweensaid first fluid passageway means and said sump tank and to permit fluidunder pressure to flow from said one pump outlet through said firstfluid passageway means to the first hydraulic unit and having a neutralposition wherein pressurized fluid delivered thereto by said pumpassembly is returned to said sump tank, second fluid passageway meansextending between the other of said pump outlets and said first fluidpassageway means, and second valve means operable to interruptcommunication between said first and second fluid passageway means andsaid sump tank and to permit fluid under pressure to flow from both saidpump outlets through said first and second fluid passageway means to thesecond hydraulic unit when said first valve means is in neutralposition.

3. A hydraulic system for controlling actuation of first and secondhydraulic units comprising the combination of a pump assembly having twoseparate outlets and an inlet connected with a sump tank, first fluidpassageway means extending between one of said pump outlets and saidsump tank, first valve means operable to interrupt communication betweensaid first fluid passageway means and said sump tank and to permit fluidunder pressure to flow from said one pump outlet through said firstfluid passageways means to the first hydraulic unit and having a neutralposition wherein pressurized fluid delivered thereto by said pumpassembly is returned to said sump tank, second fluid passageway meansextending between the other of said pump outlets and said fluidpassageway means, second and third simultaneously actuatable valvemeans, said second valve means being operable to interrupt communicationbetween said first fluid passageway means and said sump tank and topermit fluid under pressure to flow from said one pump outlet throughsaid first fluid passageway means to the second hydraulic unit when saidfirst valve means is in neutral position, and said third valve meansbeing operable to interrupt communication between said second fluidfluid passageway means receives fluid under pressure from both of saidpump outlets.

4. A hydraulic system for controlling actuation of first and secondhydraulic units comprising the combination of a pump assembly having twoseparate outlets and an inlet connected with a sump tank, a valvehousing having first and second valve means therein, first fluidpassageway means extending between one of said pump outlets and saidvalve housing, second fluid passageway means extending between the otherof said pump outlets and said valve housing, third fluid passagewaymeans extending between said valve housing and the first hydraulic unit,fourth fluid passageway means extending between said valve housing andthe second hydraulic unit, fifth fluid passageway means extendingbetween said valve housing and said sump tank, said first and secondfluid passageway means normally communicating with said fifth fluidpassageway means through said valve housing, said first valve meansbeing operable to interrupt communication between said first and fifthfluid passageway means and to place said first and third fluidpassageway means in communication and having a neutral position whereinpressurized fluid delivered thereto by said pump assembly is returned tosaid sump tank, and said second valve means being operable to interruptcommunication between said first, second and fifth fluid passagewaymeans and to place said first and second fluid passageway means incommunication with said fourth fluid passageway means when said firstvalve means is in neutral position.

5. A hydraulic system for controlling actuation of a first hydraulicunit requiring a relatively small fluid flow and a second hydraulic unitrequiring a relatively large fluid flow comprising the combination of apump assembly having two separate outlets and an inlet connected with asump tank, a valve housing having first, second and third valve meanstherein, first fluid passageway means extending between one of said pumpoutlets and said valve housing, second fluid passageway means extendingbetween the other of said pump outlets and said valve housing, thirdfluid passageway means extending bet-ween said valve housing and thefirst hydraulic unit, fourth fluid passageway means extending betweensaid valve housing and the second hydraulic unit, fifth fluid passagewaymeans extending between said valve housing and said sump tank, saidfirst and second fluid passageway means normally communicating With saidfifth fluid passageway means through said valve housing, said firstvalve means being operable to interrupt communication between said firstand fifth fluid passageway means and to place saidfirst and third fluidpassageway means in communication and having a neutral position whereinpressurized fluid delivered thereto by said pump assembly is reutrned tosaid sump tank, and said second and third valve means being operablesimultaneously to interrupt communication between said first, second andfifth fluid passageway, means and to place said first and second fluidpassageway means in communication with said fourth fluid passagewaymeans when said first valve means is in neutral position.

References Cited in the file of this patent UNITED STATES PATENTS HenryDec. 28, 1937 Lindgren Ian. 12, 194-3 Ulinski May 29, 1951 Carlson June30, 1953 Moon Oct. 20, 1953

